AGM batteries persisting at low voltage

[Marathon1150]

We have recently crossed from Mexico to the Marquesas, taking 29 days to do so. We have been anchored in Taiohae Bay, Nuku Hiva, our first landfall for a week. We have 400 watts of solar and a wind generator. Two nights ago, the battery voltage (as displayed on a BEP monitor) dropped to 10.8v. Since then, unless there is power going into the batteries (engine, solar, wind) they are hovering at 11.8 or 11.9 overnight. Normally this should indicate depleted batteries but the fridge continues to start and run.

We are planning to disconnect the batteries and measure individual voltage (2 x Lifeline AGM 4D) that are 2 years old but I am taking advantage of being on shore to send this message now.

Strangely, the BEP says we are at 100% in terms of amp hours.

Also, our fridge control unit failed about 2 days out and was replaced with a used unit by a local shop earlier in the week.

Any thoughts regarding this problem would be much appreciated. For example, is there a chance that the new fridge controller has a short or is this a coincidence?

Or are we experiencing the difficulty of getting batteries up to full charge when away from the dock for a long period of time?

Or, are the batteries bad?

Many thanks

Nello

[nhschneider]

First, congratulations on the successful passage.

Second, I think you need to do a load test on your batteries as a first step in diagnosing the problem. I seriously doubt that a short in your refrigeration system could cause the drain but that’s not to say that your refrigeration isn’t part of the problem. With the high ambient temperatures of the tropics, your refrigeration system is working overtime trying to get heat out of your food and beer. You probably don’t want me to launch into a discussion on the advantages of thick and efficient insulation but many amp hours from over-worked batteries are wasted on inadequate insulation. I fully realize that where you are right now isn’t where you want to rebuild your refrigeration compartment but it might be something you’ll want to consider in the not-too-distant future.

Fair winds and calm seas.

[Davy J]

This might help you, it seems that if you get AGM's discharged too low, they have a harder time recovering than other types:

http://https://www.optimabatteries.com/en-us/support/charging/resuscitate-deeply-discharged-battery

I used "option 2" to get two group 31's back into line. That was four years ago, still going strong.

[a64pilot]

Call Lifeline if you can, or send them an email if you can’t.
I have found them to be extremely responsive, and they will likely tell you a charge procedure to help recover your batteries.

Yes, I can believe the battery monitor was saying 100%, I’d go so far as to say that they kill more banks than they save, most chronically lie.
Only one I know of is a set and forget, the rest have to be frequently reset. The Marine how to site goes into that as well.
Go here and read the articles on batteries, there is a lot of Lifeline info here
https://marinehowto.com

Also here
https://lifelinebatteries.com/knowledge-center/

Download your battery manual here and read it, it’s the best battery manual I have ever seen, pay particular attention to the section on charging
http://lifelinebatteries.com/wp-cont...cal-Manual.pdf


Your batteries are Lifeline batteries, and are usually considered to be a premium AGM battery.
I would not go by anything not specified by Lifeline as other AGM batteries are constructed differently and likely have different voltages etc.
Just as a for instance you can equalize a lifeline battery, most other AGM’s you cannot, and I’d suspect you may need to equalize yours, and get into a habit of doing so every month or two.

[NYSail]

You can equalize your lifelines....... call them up and they will tell you the voltage...... think it’s 15.5 but double check with them. if during your passage you never brought them back up to full charge you may have over taxed them..... equalizing them may help save them.

Greg

[sailinglegend]

Originally Posted by Marathon1150

...are the batteries bad?......

It's unlikely to be the Lifeline AGMs - mine lasted 14 years as a liveaboard - but you can even kill Lifelines, like all lead acid batteries, if you don't charge them properly and get them to 100% at least once every 10 days. Clearly don't rely on you Battery monitor.

So things to check.

1. The fridge engineer could have moved a wire or left a charging cable disconnected. Maybe he connected the new fridge directly to the batteries and not via the shunt so it's not reading its discharge Ah.
2. So check that current is being drawn from the batteries by individually turning every load on and off to check the current drawn. Start with the fridge.
3. Check that ALL charging sources are putting current into the batteries - isolate each one by individually turning them on - Alternator and shorepower should give at least 100 amps each for 410 Ah of Lifelines - check wind and solar, 400 watts of solar is not enough for your kind of sailing unless you also have a genset.

It sounds like you may have been killing your expensive batteries by severely undercharging them and not monitoring them regularly. If you have a battery monitor them you need to monitor that regularly - maybe 10 times a day.

[Marathon1150]

Many thanks to all for the helpful and well considered advice. Much appreciated! We will not have access to shore power for another 10 days or so thus we will need to use the solar panels to try and equalize the batteries. The Blueskies solar controller, I believe, can be set up to do this. There are certainly some important lessons learned coming out of this experience. Many thanks again to all.

[a64pilot]

Your not going to be able to equalize batteries on Solar.
Reason is to equalize you need to hold 15.5V for four hours AFTER the batteries are fully charged, and it’s unlikely you can get fully charged just off of Solar. I guess you could motor all night and if you have an external regulator and if it’s set up correctly then by morning you are fully charged, and then you could equalize on Solar.

My recommendation is to set your Solar controller up to hold absorption voltage and don’t let it drop to float at all, then fully charge and equalize once on shore power. Often the easiest way to do that is to set your float voltage at absorption voltage, which is 14.3V for you. If your controller won’t allow the same voltages to be both, set absorption to 14.4V and float to 14.3V. That is within Lifelines recommended limits.
Remember your not fully charged until your bank is only accepting .5% of its rated capacity at absorption voltage, as an example for my 660AH bank that is 3.3 amps.
To get there my bank has to be held at absorption voltage for hours after my battery monitor says 100%.
On your AGM bank, watching trailing amps charge at absorption voltage is the ONLY way to ensure your fully charged.

You may want to look into a Balmar smart gauge, to my knowledge it’s the only set and forget battery monitor, and is also the most accurate, and easiest to use.

[sailorboy1]

Originally Posted by Marathon1150

Since then, unless there is power going into the batteries (engine, solar, wind) they are hovering at 11.8 or 11.9 overnight.

measured by what and where?

[hellosailor]

Nello, I would contact Lifeline to ask their advice on testing, and to see if you might be under wararanty. Sometimes a day makes a difference, sometimes a vendor will make an accomodation even out of warranty. And if you bought them on a credit card--check to see if that doubles an initial one year warranty and makes it into two.

But yes, something is wrong, divide and conquer, see if it is one or both, or something else in the charging systems.

[Paul L]

Originally Posted by a64pilot

Your not going to be able to equalize batteries on Solar.
.....

One way would be to isolate one battery at a time. Use solar one day to charge only the isolated battery and the next day to equalize. Use the other as the temporary house battery. Then switch.

[NYSail]

Never says but do you have a generator.... on board genset or even a honda 2000?

That would achieve the equalization at sea.

Greg

[a64pilot]

Originally Posted by Paul L

One way would be to isolate one battery at a time. Use solar one day to charge only the isolated battery and the next day to equalize. Use the other as the temporary house battery. Then switch.

Then you kill the other battery overnight.

[a64pilot]

Originally Posted by NYSail

Never says but do you have a generator.... on board genset or even a honda 2000?

That would achieve the equalization at sea.

Greg

That’s the answer. Some seem to hate the little Honda’s, but as long as you use them responsibility, they are in my opinion indispensable. I have a built in Diesel, but use the Honda far more as I rarely need the extra power the Diesel is capable of.

Plus in truth the stability as far as hz and voltage is better on the Honda than my Diesel, no matter what, the Honda outputs exactly 60hz. And 120ish volts.

[landlockedgm]

Take your volt meter and see what you really have. All that fancy stuff is nice but most over think it. Your handheld Fluke will tell you what is really going on!